When the Dallas Mavericks and Detroit Pistons fired Avery Johnson and Flip Saunders, respectively, last spring, the two coaches joined an exclusive club. It's extremely rare for teams as successful as the Mavericks and Pistons to change coaches, but even more uncommon for them to do so by choice.

When the moves first went down, I asked Basketball-Reference.com's Justin Kubatko to pull the historical data for me. According to Kubatko's research, going back to 1983, just 22 50-win teams had changed coaches before the following season. However, a number of those changes involved coaches retiring, voluntarily resigning or jumping ship for another team. Narrow it down to situations where the coach was forced out, and Johnson and Saunders are just the seventh and eighth such coaches in the last quarter-century.

Overall, the 50-win teams that changed coaches did not do nearly so well the following season. On average, they dropped from 54.8 wins to 48.2 wins, and just seven of the 22 teams improved upon their record after changing coaches. While this is a larger sample, it's the cases where the coach was forced out that are more interesting and relevant. In some of the cases of voluntary coaching changes, the coach saw the team's run coming to an end and got out while the time was right--draw your own conclusions about whether Mike D'Antoni's move from Phoenix to New York qualifies. In others, the coach's departure left the team without an adequate replacement and that was responsible for a drop-off.

In five of the other six examples, teams felt a coaching change could help them reach the next level. The one exception here is Phil Jackson, who was ushered out in Chicago after the Bulls won their sixth NBA championship in eight years. Replacing Jackson with Tim Floyd guaranteed a rebuilding effort, and while no one save Jerry Krause would rather have Floyd on the sideline than Jackson, the team's 41-win drop-off had little to do with coaching.

As for the other five teams, three of them improved their record the following season, and as a group they declined by an average of just 2.0 wins. But did the coaching changes ultimately work? Evaluating that requires us to look at each one on a case-by-case basis.

1990, Boston Celtics replace Jimmy Rodgers with Chris Ford. In his two years at the helm in Boston, Rodgers led the Celtics to a pair of first-round exits. The first was understandable because Larry Bird was limited to six games all year by surgery to remove bone spurs from his heels. Even with a healthy Bird the next year, Boston was upset by New York and that was it for Rodgers. In the first season under Ford, the Celtics improved by five games to 56 wins and advanced to the semifinals before falling to the lower-seeded Pistons. By that point, the team was clearly showing signs of age. Boston lost in the semis again the following year to Cleveland and wouldn't reach those heights again under Ford, though it had little to do with the coach.

1998, Seattle SuperSonics replace George Karl with Paul Westphal. Karl wasn't fired, but his contract was allowed to expire following a 61-win season that saw the Sonics lose to a Lakers team with an identical record in the West semifinals (the Sonics did have home-court advantage in the series). Personal conflicts with Sonics President and GM Wally Walker and owner Barry Ackerley were the primary reason for the decision, but the Sonics had underachieved in the postseason outside of their trip to the 1996 NBA Finals. The team's role players were aging, though stars Gary Payton and Vin Baker remained in their prime--until Baker came back from the lockout overweight and was never the same. The Sonics went .500 in the 50-game lockout season and missed the playoffs, and Westphal was certainly a major factor in that drop-off, making bizarre decisions with his lineup. He would last less than a month into his third season at the helm, though in fairness Westphal's willingness to trust his young players did help the Sonics develop players like Rashard Lewis and Desmond Mason.

2001, Portland Trail Blazers replace Mike Dunleavy with Maurice Cheeks. If there's a comparison to be made between this group and a modern team it's the early-oughts Blazers and the current Suns. Like Phoenix, Portland had been very competitive in the West but was unable to reach the NBA Finals. Not unlike the Suns dealing for Shaquille O'Neal, in large part to match up with the Spurs, the Blazers sought to better combat O'Neal in L.A. by trading Jermaine O'Neal for Dale Davis, and Brian Grant for Shawn Kemp. For both teams, the season ended in a first-round matchup with the nemesis, who dispatched of them with surprising ease (the Blazers were swept 3-0 by the Lakers). Replacing Dunleavy with Cheeks ultimately did little either way; the Blazers went from 50 wins to 49 and met an identical postseason fate, swept by L.A. again. Portland won another 50 games the following year, but never seriously contended in the West after their fourth-quarter collapse in Game Seven of the Western Conference Finals.

2003, Detroit Pistons replace Rick Carlisle with Larry Brown. Carlisle reportedly alienated people in the Detroit organization, but his postseason record was spotty, too. The Pistons were upset by Boston in the semifinals in 2002. The following year, they advanced to the Eastern Conference Finals but were swept by New Jersey despite home-court advantage. Under Brown, Detroit was on a similar pace the following season before stealing Rasheed Wallace at the trade deadline. The Pistons then morphed into one of the best defensive teams the league has ever seen and went on to surprise the Lakers in the NBA Finals and win the championship. They made the Finals again the following year, but by that point Brown's wandering eye had already turned elsewhere; he ended up coaching the Knicks. Detroit made another regular-season jump under Saunders the following year, but lost in the Eastern Conference Finals three straight years, bringing Saunders' tenure to an end.

2007, Houston Rockets replace Jeff Van Gundy with Rick Adelman. In firing Van Gundy and hiring Adelman, the Rockets went from arguably the league's best defensive coach to an offensive-minded one who has been underrated defensively. After winning 52 games in 2006-07, Houston won 55 games last season, aided by 22 in a row. It was their best record since 1996-97, achieved despite playing much of the season without Yao Ming. The Yao-less squad could not, however, get out of the first round. Now, Adelman appears to have the best Rockets squad in recent memory with the addition of Ron Artest. We'll see whether the team can advance deep into the postseason.

This limited group of historical examples indicates that there are a wide range of possibilities for successful teams that choose to make coaching changes. Detroit is the clearest success story, the Sonics the biggest failure. The other three teams fall somewhere in between. For the most part, however, the past suggests coaches take a backseat to the quality of the roster when these teams either reach the next level or slip into mediocrity. Was Brown an upgrade for the Pistons? Yes, but the gain was not nearly as significant as adding Wallace to the lineup. From the opposite perspective, Westphal might have been successful in Seattle had Baker continued to play at an All-Star level.

So, while there's plenty of talk out of the Dallas and Detroit training camps about how much players like their new coaches' contrasting styles (Michael Curry is tightening the ship with the Pistons, while Rick Carlisle is perceived to be more of a players' coach for the Mavericks), you can largely tune out those happy noises. The two teams are also alike in that neither made wholesale offseason roster changes. Detroit can still point to the development of young players like Amir Johnson, Jason Maxiell and Rodney Stuckey as a reason for optimism. Dallas looks to be much more reliant on a coaching upgrade, the kind that hasn't worked regularly in the past.

Kevin Pelton is an author of Basketball Prospectus.
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